It’s almost here. Let’s run down what we can expect for Maine and New Hampshire, December through February.
— Warmer than normal.
— Above normal precipitation.
— Normal or slightly above normal snowfall.
— Snow on the ground Christmas morning In Portland.
— January or late December cold snap with temps 10 to 30 below zero.
— January thaw.
— February warmest month relative to normal.
— Above normal snowfall March.
When forecasting winter in Maine, a good place to start is about 3,000 miles away in the Pacific. It’s expected to be a La Nina winter, and that means ocean temperatures in the equatorial Pacific are expected to be cooler than normal.
Another hint to our winter weather can also be found in the warmer than normal waters north of Hawaii and also in portions of the North Pacific.
I analyzed 10 winters that showed a version of both of these variables including La Nina -0.5 to -1.5. They are:
These ocean anomalies often have an effect on the strength and position of the jet stream during the winter months. Most important to us, is an active polar jet that ridges in the pacific and dips into the northern half of the United States.
That configuration in the jet stream can put the coldest air in the northern Hemisphere in Canada. You can see how those 10 winters resulted in an upper air pattern that placed cold temperatures in southern Canada and the northern tier of the U.S.
Here’s a closer look at the temperature anomalies for the U.S. for the La Nina winters outlined above in December through February.
Here’s the breakdown by month. Take note that the coolest relative to normal is December. February averages warmest relative to normal.
La Nina winters usually bring above normal precipitation to Maine. Of the 10 La Nina winters analyzed, 100 percent of them showed either normal or above normal precipitation in Vacationland. The years averaged out like this:
January and February showed big variability in precipitation. When isolating December, a consistent spike in precipitation is present.
And that usually translates to snow as well. Ninety percent of the La Nina years analyzed had either normal or above normal snowfall in Portland during the month of December.
For our friends who like to ski and snowboard, there is a correlation between La Nina winters and big snow years. Check out this snow data from Sugarloaf Ski Resort. Four of the five top snow years over the past two decades occurred in La Nina winters (or La Nina transitioning to neutral).
This is true at the Mount Washington Observatory as well. Four of the five top snow years over the past two decades were either La Nina or weak La Nina to neutral.
Sarah Long over at WMTW and I can guarantee accuracy in those 2000-01 and 2001-02 snow measurements.
This winter’s La Nina is expected to be moderate -0.5 to -1.5. There are subtle changes in La Nina snowfall in New England based on the strength of the La Nina. Here’s the breakdown. Note the higher probability of above normal snow in northern New England.
While El Nino Southern Oscillation is a great starting point for forecasting seasonal weather, there are a ton of other teleconnections worth investigating. The Arctic Oscillation is always something we need to monitor during the winter months.
Big temperature swings and often stormy patterns in winter can usually occur when we have a negative Arctic Oscillation. When the AO is in its negative phase, cold temps near the pole can dip much farther south than when the AO is in a positive phase. Last winter the AO was in a positive phase which kept the cold temps locked up near the pole.
Seventy percent of the La Nina winters analyzed showed a negative Arctic Oscillation in January. The La Nina in January of 2009 and the more recent of Jan. 1, 2018, had AOs in its negative phase or neutral trending negative. Who remembers New Year’s Day 2018? The temperature got down to 30 below in my backyard that morning (yes, I still use my Radio Shack thermometer). It was the coldest morning in 15 years in Portland. My peach tree died because of that cold as well (it’s still a sore subject).
The Maine State record of -50 degrees on Jan. 16, 2009, was also a La Nina winter and had a neutral AO trending negative by February.
Those cold shots did not have longevity to them like in 2015. Instead, they came and went. I anticipate this winter will have big temperature fluctuations as well with the warm winning out.
Of the 10 winters analyzed, 70 percent had a negative arctic oscillation in January. I’m betting in this expected warm winter, there will be at least one good cold shot very early in 2021.
Now might be a good time to bring some computer model guidance into the conversation. It’s worth mentioning seasonal computer model guidance did a poor job last winter. Here are some seasonal models outlining temperature and precipitation anomaly December through February.
Finally, throughout the summer and fall, we’ve noticed unusual similarities between 2020 and 2011 in Portland and beyond. It has become quite a joke in the weather office. This is the fun short list Matt Hoenig and I came up with off the tops of our heads.
As a snow lover, I’ve been referring to this unusual comparison as the 2011 curse. The reason, winter 2011-12 had only 72 percent of normal snowfall, and was 5 degrees warmer than normal. Upper air patterns and even ocean water temperature anomalies are quite a bit different this fall compared to 2011.
If you’ve stuck with this so far, I should be offering you a beer or free car wash or something. Thanks! Here’s the CliffsNotes of how I expect this winter to go down.
— Off to a quick start in December. Ninety percent chance normal or above normal snowfall in December.
— Above normal precipitation December through February.
— Seventy percent chance normal or above normal snowfall.
— Eighty percent chance there’s snow on the ground in Portland on Christmas morning. Any given year it’s a 53 percent chance.
— Early January or late December cold snap with temps 10 to 30 below zero.
— Seventy percent chance January thaw with temps 50 degrees or warmer.
— February warmest relative to normal.
— Seventy percent chance normal or above normal snowfall in March.
— End to the drought.
— Ninety-nine percent chance the Patriots don’t win the Super Bowl.
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